US20130337344A1 - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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US20130337344A1
US20130337344A1 US13/983,946 US201213983946A US2013337344A1 US 20130337344 A1 US20130337344 A1 US 20130337344A1 US 201213983946 A US201213983946 A US 201213983946A US 2013337344 A1 US2013337344 A1 US 2013337344A1
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ion secondary
lithium ion
secondary battery
fluorine
active material
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Kayo Mizuno
Keiichi Hayashi
Masaaki Suzuki
Takayuki Hirose
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Toyota Industries Corp
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Toyota Industries Corp
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Assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI reassignment KABUSHIKI KAISHA TOYOTA JIDOSHOKKI ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HAYASHI, KEIICHI, HIROSE, TAKAYUKI, MIZUNO, Kayo, SUZUKI, MASAAKI
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a lithium ion secondary battery.
  • LiCoO 2 lithium cobalt oxide
  • a carbon-based material as the negative electrode material
  • Such lithium ion secondary batteries are being notably used as the power source in a wide range of fields because of their high energy density as well as size and weight reduction potential.
  • the production of LiCoO 2 which uses cobalt that is a rare metal (minor metal), will likely be faced with a serious shortage of resource in future.
  • development of a material for the positive electrode that is inexpensive and stably supplied has been sought after.
  • Lithium manganese composite oxides are considered to be potentially attractive as they are made up of inexpensive elements and manganese (Mn) in their basic composition can be stably supplied.
  • Li 2 MnO 3 that contains only tetravalent manganese ions and no trivalent manganese ions that cause elution of manganese during charge and discharge is attracting attention.
  • Batteries using Li 2 MnO 3 have been thought to be not able to be charged and discharged. However, recent research has shown that such batteries, if charged to 4.8 V, can exhibit charge/discharge reversibility. Even so, there is still much scope for improvement in charge and discharge characteristics of batteries using Li 2 MnO 3 .
  • Li 2 MnO 3 and LiMeO 2 (Me being a transition metal element), xLi 2 MnO 3 .(1-x)LiMeO 2 (0 ⁇ x ⁇ 1), is being actively researched as a possible material that can improve the charge and discharge characteristics.
  • Li 2 MnO 3 can also be represented by the general formula Li(Li 0.33 Mn 0.67 )O 2 , and is known to have the same crystal structure as that of LiMeO 2 . Therefore, xLi 2 MnO 3 .(1-x) LiMeO 2 can sometimes be expressed as Li 1.33-y Mn 0.67-z Me y+z O 2 (0 ⁇ y ⁇ 0.33, 0 ⁇ z ⁇ 0.67).
  • a lithium ion secondary battery that uses a lithium manganese composite oxide containing tetravalent manganese ions as the positive electrode active material needs to be charged before use so as to activate the positive electrode active material.
  • lithium ions are released from the positive electrode active material of the lithium manganese composite oxide and oxygen is desorbed, whereby the non-aqueous electrolyte solution undergoes oxidative degradation.
  • Another problem was that when stored in a charged state in a high temperature storage test, the non-aqueous electrolyte solution degrades on the surface of the positive electrode, as the positive electrode side is placed in an oxidizing atmosphere.
  • the non-aqueous electrolyte solution undergoing oxidative degradation forms an insulating film on the electrode surface, whereby the internal resistance is increased and the charge and discharge capacity after the storage is lowered.
  • Japanese Unexamined Patent Application Publication No. 2004-296315 discloses a technique of using a lithium-containing composite oxide such as LiCoO 2 or LiNiO 2 , which has high-voltage and high-capacity potential, as the positive electrode active material, and a lithium salt containing fluorine and a group 2 element salt containing fluorine as the electrolytic salt (supporting electrolyte) of the non-aqueous electrolyte solution.
  • a lithium-containing composite oxide such as LiCoO 2 or LiNiO 2 , which has high-voltage and high-capacity potential
  • a lithium salt containing fluorine and a group 2 element salt containing fluorine as the electrolytic salt (supporting electrolyte) of the non-aqueous electrolyte solution.
  • 2008-16424 discloses a technique of using a non-aqueous electrolyte solution, which includes an electrolytic salt containing lithium borate and fluorine, and a non-aqueous solvent containing fluorine (such as fluoroethylene carbonate), in a lithium ion secondary battery.
  • a non-aqueous electrolyte solution which includes an electrolytic salt containing lithium borate and fluorine, and a non-aqueous solvent containing fluorine (such as fluoroethylene carbonate), in a lithium ion secondary battery.
  • graphite is used as the negative electrode active material.
  • the solvent in the non-aqueous electrolyte solution undergoes reductive degradation on the surface of the negative electrode while charging and forms an insulating film called SEI (Solid Electrolyte Interface) on the negative electrode surface.
  • SEI Solid Electrolyte Interface
  • the SEI is mainly composed of LiF, LiCO 3 , and the like. As lithium is irreversibly coupled on the inside these substances, formation of the SEI reduces the amount of lithium available for charging and discharging and increases the irreversible capacity. Formation of SEI would also cause the problem of increased internal resistance of the battery.
  • the present invention was made in view of these circumstances, its object being to reduce oxidative and reductive degradation of non-aqueous electrolyte solution in a lithium ion secondary battery with a positive electrode active material that has high-capacity potential but requires an activation process.
  • the present invention provides a lithium ion secondary battery, including: a positive electrode including a positive electrode active material made of a lithium manganese based oxide containing lithium (Li) and tetravalent manganese (Mn) and having a crystal structure known as a layered rock salt structure; a negative electrode including a negative electrode active material made of a silicon oxide represented by SiO x (0.3 ⁇ x ⁇ 1.6); and an electrolyte including a non-aqueous solvent and an electrolytic salt, the electrolyte containing fluorine (F) in at least one of the non-aqueous solvent and the electrolytic salt.
  • a positive electrode including a positive electrode active material made of a lithium manganese based oxide containing lithium (Li) and tetravalent manganese (Mn) and having a crystal structure known as a layered rock salt structure
  • a negative electrode including a negative electrode active material made of a silicon oxide represented by SiO x (0.3 ⁇ x ⁇ 1.6)
  • an electrolyte including
  • the lithium ion secondary battery of the present invention uses a lithium manganese based oxide that needs activation to function as the positive electrode active material.
  • the battery uses SiO x as the negative electrode active material.
  • the battery uses a non-aqueous electrolyte solution that contains fluorine (F) in at least one of the non-aqueous solvent and the electrolytic salt.
  • fluorine element (F) will be referred to simply as fluorine.
  • the non-aqueous electrolyte solution containing fluorine has improved oxidation resistance. This is considered to be due to the electrophilicity of fluorine contained in the non-aqueous electrolyte solution. With the improved oxidation resistance, oxidative degradation of the non-aqueous electrolyte solution is reduced.
  • Non-aqueous electrolyte solution containing fluorine has poor reduction resistance. If graphite (MAG) is used as the negative electrode active material, for example, the electrolyte undergoes reductive degradation at edge portions of MAG. SiO x , however, does not have edge portions such as those of MAG but has an inactive silicate phase. Moreover, SiO x has a higher reaction potential than MAG. Therefore, reductive degradation of the non-aqueous electrolyte solution can be reduced by using SiO x as the negative electrode active material.
  • MAG graphite
  • the lithium ion secondary battery of the present invention oxidative degradation of the non-aqueous electrolyte solution is reduced by the use of fluorine contained in the solution, and at the same time, reductive degradation of the non-aqueous electrolyte solution is reduced despite the use of the fluorine in the solution, by the use of SiO x as the negative electrode active material. Accordingly, the lithium ion secondary battery of the present invention can reduce oxidative and reductive degradation of the non-aqueous electrolyte solution despite the use of the lithium manganese based oxide that requires activation to function as the positive electrode active material.
  • FIG. 1 is a graph showing the capacity recovery rates after high temperature storage of lithium ion secondary batteries according to Examples 1 and 2 of embodiment and a comparative example;
  • FIG. 2 is a graph showing the rate of increase in internal resistance after high temperature storage of lithium ion secondary batteries according to Examples 1 and 2 of embodiment and a comparative example.
  • the non-aqueous electrolyte solution of the lithium ion secondary battery according to the present invention contains a non-aqueous solvent and an electrolytic salt dissolved in the solvent. At least one of the non-aqueous solvent and the electrolytic salt includes fluorine.
  • the non-aqueous solvent that contains fluorine will be referred to as “fluorine-containing non-aqueous solvent”
  • the electrolytic salt that contains fluorine will be referred to as “fluorine-containing electrolytic salt”.
  • the fluorine-containing non-aqueous solvent and the fluorine-containing electrolytic salt will be referred to collectively as “fluorine-containing material”.
  • fluorine-containing electrolytic salt that can be used preferably is a lithium salt containing fluorine.
  • it is at least one of fluorine-containing lithium salts selected from a group consisting of LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 3 (C 2 F 5 ) 3 , LiPF 3 (CF 3 ) 3 , LiPF 3 (iso-C 3 F 7 ) 3 , LiPF 5 (iso-C 3 F 7 ), LiSbF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN(CF 3 SO 2 ) 2 , and LiC n F 2n+1 SO 3 (n
  • the non-aqueous electrolyte solution of the lithium ion secondary battery according to the present invention may contain an electrolytic salt other than the fluorine-containing electrolytic salt.
  • LiClO 4 , or LiI, or the like for example, either alone or as a blend of two or more, may be used with one or more of the fluorine-containing electrolytic salts listed above.
  • fluorinated ethylene carbonates such as fluorinated ethylene carbonate, difluorinated ethylene carbonate, trifluorinated ethylene carbonate, and the like
  • fluorinated ethylene carbonate is 4-fluoro-1,3-dioxolane-2-one (fluoroethylene carbonate, FEC).
  • difluorinated ethylene carbonate are 4-methyl-5-fluoro-1,3-dioxolane-2-one, and 4,5-difluoro-1,3-dioxolane-2-one, difluoroethylene carbonate (DFEC).
  • trifluorinated ethylene carbonate examples include trifluoropropylene carbonate, 4-trifluoromethyl-1,3-dioxolane-2-one, and trifluoromethylene ethylene carbonate.
  • FEC particularly, can be used preferably in terms of oxidation resistance.
  • the non-aqueous electrolyte solution of the lithium ion secondary battery according to the present invention may have a composition similar to conventional solutions except that it contains the fluorine-containing material. It may contain, for example, a non-aqueous solvent and an electrolytic lithium metal salt dissolved in the solvent.
  • a commonly known non-aqueous solvent may also be used in addition to the fluorine-containing non-aqueous solvents mentioned above.
  • Solvents containing chain esters are preferable in terms of load characteristics. Examples include organic solvents such as chain carbonates, such as, typically, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, ethyl acetates, and methyl propionates.
  • chain esters may be used either alone or as a blend of two or more.
  • the chain ester should preferably occupy 50 vol % or more, and in particular, 65 vol % or more, of the entire non-aqueous solvent, in order to improve low temperature characteristics.
  • 50 vol % or more, and in particular, 65 vol % or more, of the entire non-aqueous solvent should preferably be taken up by chain esters containing fluorinated ethylene carbonates.
  • the non-aqueous solvent should preferably include an ester having a high dielectric constant (of 30 or more) mixed in the chain ester mentioned above.
  • esters include, for example, cyclic carbonates such as, typically, ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate, ⁇ -butyrolactone, and ethylene glycol sulfite.
  • Esters having a cyclic structure, such as ethylene carbonate and propylene carbonate are particularly preferable.
  • Such esters having a high dielectric constant should preferably take up 10 vol % or more, in particular 20 vol % or more, of the entire non-aqueous solvent, taking account of the discharge capacity.
  • the ester content should preferably be 40 vol % or less, in particular, 30 vol % or less, in terms of the load characteristics.
  • the density of the electrolyte in the non-aqueous electrolyte solution should preferably be, but not particularly limited to, about 0.3 to 1.7 mol/dm 3 , and more preferably 0.4 to 1.5 mol/dm 3 .
  • the density of the electrolyte here refers to the density of the entire electrolyte including the fluorine-containing electrolytic salt(s).
  • the non-aqueous electrolyte solution may also contain an aromatic compound in order to enhance battery safety performance and storage characteristics. Examples of aromatic compounds that can favorably be used include benzenes having an alkyl radical such as cyclohexylbenzene or t-butylbenzene, biphenyls, and fluorobenzenes.
  • the density of the fluorine-containing material in the non-aqueous electrolyte solution may vary depending on the type of the fluorine-containing material. If a fluorine-containing electrolytic salt only is to be used as the fluorine-containing material, for example, it should preferably be about 1 M. If a fluorine-containing non-aqueous solvent only is to be used, the density should preferably be about 40 vol %. If a fluorine-containing electrolytic salt and a fluorine-containing non-aqueous solvent are to be used together, the density of the fluorine-containing electrolytic salt should preferably be about 1 M and the density of the fluorine-containing non-aqueous solvent should preferably be about 30 vol %.
  • the effects of the fluorine-containing material may hardly be achieved. If the content largely exceeds the above-specified value, the effects may be reduced, and in some cases the internal resistance of the lithium ion secondary battery may rise.
  • the lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte solution.
  • the battery also includes a separator interposed between the positive electrode and the negative electrode, as with commonly known lithium ion secondary batteries.
  • the positive electrode includes a positive electrode active material made of a lithium manganese based oxide containing lithium (Li) and tetravalent manganese (Mn) and having a crystal structure known as a layered rock salt structure.
  • This positive electrode active material has a basic composition of a lithium manganese based oxide represented by the formula: xLi 2 M 1 O 3 .(1-x)LiM 2 O 2 (0 ⁇ x ⁇ 1), wherein M 1 is one or more metal elements at least containing tetravalent Mn, and M 2 is two or more metal elements at least containing tetravalent Mn.
  • the lithium manganese based oxide also includes composite oxides having a slightly different composition from the above formula due to inevitable loss of L 1 , M 1 , M 2 , or O.
  • the manganese in the resultant composite oxide may have a lower average oxidation number because of the presence of Mn having a valence of less than 4, the tolerable range of valence being 3.8 to 4.
  • At least one of the metal elements selected from the group of Cr, Fe, Co, Ni, Al, and Mg may be used in M 1 and M 2 as a metal element other than the tetravalent Mn. There should preferably be 1.1 times more Li than Mn in the above formula.
  • This positive electrode active material can be manufactured by performing a material mixture preparation step of preparing a material mixture, wherein a metal compound material containing one or more metal elements at least including Mn is mixed with a molten salt material including lithium hydroxide but substantially no other compounds and containing more lithium than in the theoretical composition of the target composite oxide, and a melting reaction step of melting the material mixture so that the mixture undergoes reaction at a temperature higher than a melting point of the molten salt material.
  • a metal compound material containing one or more metal elements at least including Mn is mixed with a molten salt material including lithium hydroxide but substantially no other compounds and containing more lithium than in the theoretical composition of the target composite oxide
  • a melting reaction step of melting the material mixture so that the mixture undergoes reaction at a temperature higher than a melting point of the molten salt material.
  • This material mixture is then subjected to a high temperature of more than the melting point of the lithium hydroxide to undergo reaction in the molten salt, whereby fine particles of composite oxide are obtained. This is because the material mixture mixes with the molten salt uniformly by alkali fusion. Since the reaction occurs in the molten salt that substantially consists of lithium hydroxide, the crystal growth rate is low even under the high reaction temperature, so that a composite oxide having a primary particle size of nanometers is obtained.
  • One or more metal compounds selected from oxides, hydroxides, and metal salts containing one or more metal elements at least including Mn are used as the metal compound material that supplies tetravalent Mn.
  • the metal compound material must contain the metal compound(s).
  • Specific examples of the metal compound include manganese dioxide (MnO 2 ), manganese sesquioxide (Mn 2 O 3 ), manganese monoxide (MnO), trimanganese tetraoxide (Mn 3 O 4 ), manganese hydroxide (Mn(OH) 2 ), manganese oxyhydroxide (MnOOH), and oxides, hydroxides, and metal salts of these having part of Mn substituted with Cr, Fe, Co, Ni, Al, Mg, and the like. One of these, or two or more of these may be used as the essential metal compound(s). MnO 2 , in particular, is preferable, as relatively high purity MnO 2 is readily available.
  • Mn in the metal compound need not necessarily be tetravalent and may have a valence of less than 4. This is because the reaction progresses in a high oxidation state so that divalent or trivalent Mn eventually becomes tetravalent. The same applies to the transition elements that substitute Mn.
  • a second metal compound which is selected from oxides, hydroxides, and metal salts, may be used as the compound containing a metal element for substituting part of Mn.
  • the second metal compound include cobalt oxide (CoO, CO 3 O 4 ), cobalt nitrate (Co(NO 3 ) 2 .6H 2 O), cobalt hydroxide (Co(OH) 2 ), nickel oxide (NiO), nickel nitrate (Ni(NO 3 ) 2 .6H 2 O), nickel sulfate (NiSO 4 .6H 2 O), aluminum hydroxide (Al(OH) 3 ), aluminum nitrate (Al(NO 3 ) 3 .9H 2 O), copper oxide (CuO), copper nitrate (Cu(NO 3 ) 2 .3H 2 O), and calcium hydroxide (Ca(OH) 2 ).
  • cobalt oxide CoO, CO 3 O 4
  • cobalt nitrate Co(NO 3 ) 2 .6H 2 O
  • the melting reaction step is a step of melting the material mixture so that it undergoes reaction.
  • the reaction temperature is the temperature of the material mixture during the melting reaction step and it may be the melting point of the molten salt material or higher. With a temperature lower than 500° C., however, it is difficult to produce the desired composite oxide containing tetravalent Mn with good selectivity because of insufficient reaction activity of the molten salt. With a reaction temperature of 550° C. or higher, composite oxide with high crystallinity can be obtained.
  • the upper limit of the reaction temperature should preferably be lower than the decomposition temperature of the lithium hydroxide, not higher than 900° C., and more preferably not higher than 850° C.
  • the reaction temperature should preferably be in the range of 500 to 700° C., and more preferably 550 to 650° C. If the reaction temperature is too high, the molten salt undergoes decomposition reaction, which is not desirable. Sufficient reaction of the material mixture can be achieved if it is kept under this reaction temperature for 30 min or more, more preferably for 1 to 6 hours.
  • the melting reaction step may be carried out in an oxygen-containing atmosphere such as, for example, air atmosphere, or gas atmosphere containing oxygen and/or ozone gas, so that a single phase composite oxide containing tetravalent Mn is more readily obtained.
  • an atmosphere containing oxygen gas the oxygen density should preferably be 20 to 100 vol %, and more preferably 50 to 100 vol %. The higher the oxygen density, the smaller the particle diameter of the synthesized composite oxide tends to be.
  • the composite oxide obtained by the production method described above has the layered rock salt structure. That the composite oxide substantially has the layered rock salt structure can be confirmed by an X-ray diffraction (XRD) or electron diffraction analysis. The layered structure can also be observed in a high resolution image obtained by high-resolution transmission electron microscopy (TEM).
  • the resultant composite oxide can be represented by the formula: xLi 2 M 1 O 3 .(1-x)LiM 2 O 2 (0 ⁇ x ⁇ 1), wherein M 1 is a metal element at least containing tetravalent Mn, and M 2 is a metal element at least containing tetravalent Mn.
  • An atomic ratio of 60% or less, furthermore 45% or less, of lithium may be substituted with hydrogen (H). While M 1 should preferably be mostly tetravalent Mn, less than 50%, furthermore less than 80%, of M 1 may be substituted with other metal elements.
  • the metal elements other than tetravalent Mn constituting M 1 and M 2 should preferably be selected from Ni, Al, Co, Fe, Mg, and Ti, in terms of the charge and discharge capacities of the battery using them as the electrode material.
  • the lithium manganese based oxide also includes composite oxides having a slightly different composition from the above formula due to inevitable loss of L 1 , M 1 , M 2 , or O. Therefore, M 1 or Mn contained in M 2 may have a lower oxidation number, the tolerable range of valence being 3.8 to 4.
  • a specific example is a solid solution containing one or two or more of Li 2 MnO 3 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , and LiNi 0.5 Mn 0.5 O 2 .
  • Part of Mn, Ni, and Co may be substituted with other metal elements.
  • the resultant composite oxide as a whole may have the oxide specified herein as the basic composition, and may have a slightly different composition from the above formula due to inevitable loss of metal elements or oxygen.
  • the positive electrode of the lithium ion secondary battery according to the present invention includes a current collector and an active material layer bonded on the current collector.
  • the active material layer may be formed by mixing a positive electrode active material made of a lithium manganese based oxide having a crystal structure known as a layered rock salt structure, a conductive additive, binder resin, and a suitable amount of organic solvent added as required into a slurry, applying it on the current collector by any of roll coating, dip coating, doctor blading, spray coating, or curtain coating, and curing the binder resin after that.
  • metal mesh or foil For the current collector, it is common to use metal mesh or foil.
  • porous or non-porous conductive substrates made of a metal material such as stainless steel, titanium, nickel, aluminum, and copper, or conductive resin.
  • porous conductive substrates include mesh, net, punched sheet, lath, porous body, foam, or fibrous molded article such as non-woven fabric.
  • non-porous conductive substrates include foil, sheet, and film. Materials other than metal, such as carbon sheet or the like, may also be used for the current collector.
  • the conductive additive is added for enhancing the conductivity of the electrode.
  • any of carbon black which is fine particles of carbon, Massive Artificial Graphite (MAG), acetylene black (AB), Ketjen black (KB), vapor grown carbon fiber (VGCF) and the like can be added either alone or as a combination of two or more of these.
  • the amount of conductive additive to be used may be, as commonly known, but not limited to, about 20 to 100 parts by mass relative to 100 parts by mass of positive electrode active material.
  • the binder resin binds the positive electrode active material and the conductive additive together.
  • Any of fluorine-containing resins such as polyfluorovinylidene, polytetrafluoroethylene, or fluorine rubbers, or thermoplastic resins such as polypropylene, polyethylene, and the like may be used.
  • any of N-methyl-2-pyrrolidone (NMP), methanol, methyl isobutyl ketone (MIBK), and the like may be used.
  • the negative electrode of the lithium ion secondary battery according to the present invention includes a current collector and an active material layer bonded on the current collector.
  • a powder of silicon oxide represented by SiO x (0.3 ⁇ x ⁇ 1.6) is used. It is known that SiO x can be thermally decomposed into Si and SiO 2 . This is called disproportional reaction.
  • Homogeneous solid silicon monoxide (SiO) containing Si and O in a ratio of generally 1:1 will separate into two phases, Si phase and SiO 2 phase, as the solid reacts internally.
  • the Si phase obtained by the separation is very finely particulated.
  • the SiO 2 (silicate) phase that covers the Si phase functions to reduce degradation of the non-aqueous electrolyte solution.
  • the battery with SiO x alone as the negative electrode active material may show insufficient cycle characteristics, in which case it may be desirable to use other carbon materials such as MAG in combination with SiO x .
  • the current collector, conductive additive, binder resin, and organic solvent for the positive electrode can also be used for the negative electrode.
  • the separator should preferably have sufficient strength and a large capacity to hold non-aqueous electrolyte solution.
  • the lithium ion secondary battery with the composite oxide mentioned above as the positive electrode active material and the fluorine-containing material mentioned above in the non-aqueous electrolyte solution has excellent stability, so that the battery can be operated stably even with the use of such a thin separator.
  • the lithium ion secondary battery configured with the elements described above may have various shapes such as cylindrical, laminated, coin-shaped, and so on.
  • an electrode assembly is formed, with the separator interposed between the positive electrode and the negative electrode.
  • Positive and negative current collectors are connected to positive and negative terminals that extend to the outside with current collecting leads or the like, and this electrode assembly is impregnated with the non-aqueous electrolyte solution described above and sealed in a battery case, to form the lithium ion secondary battery.
  • the battery is first charged to activate the positive electrode active material. Since the battery uses a positive electrode active material made of a lithium manganese based oxide having a layered rock salt structure, lithium ions are released and oxygen is generated during the initial charge. Therefore, the charge should preferably be performed before sealing the battery case.
  • the lithium ion secondary battery of the present invention described above can favorably be used in the fields of communication equipment or information-related equipment such as mobile phones and personal computers, as well as in the field of automobiles.
  • the lithium ion secondary battery can be used as the power source of an electric car, for example, by being mounted in a vehicle.
  • the target product is Li 2 MnO 3
  • the ratio of Li in the target product to Li in the molten salt material was 0.2 (0.04 mol/0.2 mol), assuming that Mn in the manganese dioxide was all supplied to Li 2 MnO 3 .
  • the material mixture was put in a crucible, which was placed inside an electric furnace of 700° C., and the mixture was heated at 700° C. for two hours in vacuum.
  • the material mixture melted into molten salt, with a black product precipitated.
  • the crucible containing the molten salt was then cooled down to room temperature inside the electric furnace, after which it was taken out of the electric furnace.
  • the entire crucible was immersed in 200 mL ion exchange water, and the content was stirred to dissolve the solidified molten salt into water.
  • the resultant liquid was a black suspension.
  • the black suspension was filtered to obtain clear filtrate and a black solid material on the filter paper. The filtered material was thoroughly cleaned with acetone and further filtered.
  • the black solid substance after the cleaning was dried at 120° C. for twelve hours in vacuum, after which it was pulverized with the use of a mortar and pestle.
  • the black powder thus obtained was subjected to an X-ray diffraction (XRD) measurement using CuK ⁇ .
  • XRD X-ray diffraction
  • the XRD measurement revealed that the resultant black powder had a layered rock salt structure.
  • the composition of the resultant black powder was confirmed to be Li 2 MnO 3 .
  • valence of Mn was carried out as follows: A 0.05 g sample was put in a triangular flask, an accurately measured amount (40 mL) of 1% sodium oxalate solution was added, and 50 mL of H 2 SO 4 was further added, after which the sample was dissolved in a water bath at 90° C. in a nitrogen gas atmosphere. Potassium permanganate (0.1 N) was dropped to this solution until the solution took a pinkish color which indicated the end point of the titration (titration amount: V 1 ).
  • Amount of active oxygen (%) ⁇ (2 ⁇ V 2 ⁇ V 1 ) ⁇ 0.00080/amount of sample ⁇ 100.
  • the average valence of Mn was then calculated from the amount of Mn in the sample (ICP measured value) and the amount of active oxygen.
  • the positive electrode active material thus obtained Ketjen black (KB) as a conductive additive, and polyfluorovinylidene (PVdF) as a binder resin were mixed at a mass ratio of 88:6:6. This mixture was then coated on a sheet-like current collecting aluminum foil. The current collecting foil coated with the mixture was dried at 120° C. for more than 12 hours in vacuum. A nickel tab was attached to a corner portion of the current collecting foil by resistance welding. This corner portion was covered with a resin film.
  • a powder of SiO (made by Sigma-Aldrich Japan, mean particle diameter of 5 ⁇ m) was heated at 900° C. for two hours to prepare a powder of SiO with a mean particle diameter of 5 ⁇ m.
  • homogeneous solid silicon monoxide (SiO) containing Si and O in a ratio of generally 1:1 separates into two phases, Si phase and SiO 2 phase, as the solid reacts internally.
  • the Si phase obtained by the separation is very finely particulated.
  • SiO x powder To 42 parts by mass of the thus obtained SiO x powder were mixed 40 parts by mass of MAG powder and 3 parts by mass of Ketjen black (KB) powder as conductive additives, and polyamideimide (PAI) as a binder resin, to prepare a slurry.
  • This slurry was applied on the surface of a 20 ⁇ m thick electrolytic copper foil (current collector) using a doctor blade, to form a negative electrode active material layer on the copper foil. This was followed by drying at 80° C. for 20 minutes to remove the organic solvent from the negative electrode active material layer by volatilization.
  • the current collector and the negative electrode active material layer were firmly joined together with a roll press. This was heated at 200° C. for two hours to set, to form an electrode with an active material layer of about 15 ⁇ m.
  • a nickel tab was attached to a corner portion of the negative electrode by resistance welding. This corner portion was covered with a resin film.
  • Fluoroethylene carbonate fluorine-containing non-aqueous solvent
  • LiPF 6 fluorine-containing electrolytic salt
  • FEC fluoroethylene carbonate
  • EMC ethyl methyl carbonate
  • a laminated cell was fabricated using the positive electrode, the negative electrode, and the non-aqueous electrolyte solution described above.
  • the laminated cell was configured with an electrode plate assembly made up of positive and negative electrodes and a separator, a laminate film enveloping and sealing the electrode plate assembly, and the non-aqueous electrolyte solution poured into the laminate film.
  • the electrode plate assembly was formed by stacking one negative electrode upon one positive electrode, with one separator interposed therebetween.
  • the positive and negative electrodes are configured as described above.
  • the separator is a rectangular, polypropylene resin sheet.
  • the electrode plate assembly was formed such that the positive electrode, separator, and negative electrode were stacked upon one another in this order, with the active material layers of positive and negative electrodes facing each other via the separator.
  • the laminate film that enveloped and sealed the electrode plate assembly was bag-shaped, with four sides air-tightly sealed.
  • the tabs of both electrodes partly extend to the outside from one of the four sides of the laminate film for external electrical connection.
  • the laminate film is filled with the non-aqueous electrolyte solution described above.
  • the laminated cell was thus formed, by inserting the electrode plate assembly into the bag-shaped laminate film with three sealed sides, filling the laminate film with the non-aqueous electrolyte solution, and sealing the remaining one side.
  • the cell was then subjected to constant current constant voltage charge (0.2 C, 4.6 V) to activate the positive electrode active material, and was complete as a lithium ion secondary battery.
  • a high temperature storage test of storing the lithium ion secondary battery at 80° C. for five days was carried out.
  • the 1 C discharge capacity before the high temperature storage test, and the 1 C discharge capacity after a charge up to an SOC of 100% following full discharge after the high temperature storage were measured, and the capacity recovery rate was calculated from the following equation.
  • Capacity recovery rate 100 ⁇ (1 C discharge capacity after a charge up to an SOC of 100% following full discharge after storage)/(1 C discharge capacity before storage)
  • a high temperature storage test of storing the lithium ion secondary battery at 80° C. for five days was carried out.
  • the battery internal resistances before and after the high temperature storage test were measured, and the rate of increase in the internal resistance was calculated from the following equation.
  • Rate of increase in internal resistance 100 ⁇ (resistance after storage ⁇ resistance before storage)/resistance before storage
  • a lithium ion secondary battery was fabricated similarly to Example 1, except that the non-aqueous solvent of the non-aqueous electrolyte solution was made of EC and EMC and did not contain FEC.
  • the lithium ion secondary battery of Example 2 contains Li 2 MnO 3 as the positive electrode active material, SiO x as the negative electrode active material, and a fluorine-containing electrolytic salt (LiPF 6 ) in the non-aqueous electrolyte solution, while it does not contain a fluorine-containing non-aqueous solvent (FEC).
  • the capacity recovery rate and the rate of increase in internal resistance were calculated similarly to Example 1, except that the battery used was this lithium ion secondary battery. The results are shown in FIG. 1 and FIG. 2 , respectively.
  • a lithium ion secondary battery was fabricated similarly to Example 1, except that the negative electrode active material was made of MAG alone.
  • the lithium ion secondary battery of Comparative Example contains Li 2 MnO 3 as the positive electrode active material, MAG as the negative electrode active material, and a fluorine-containing electrolytic salt (LiPF 6 ) and a fluorine-containing non-aqueous solvent (FEC) in the non-aqueous electrolyte solution, while it does not contain SiO x as the negative electrode active material.
  • LiPF 6 fluorine-containing electrolytic salt
  • FEC fluorine-containing non-aqueous solvent
  • the capacity recovery rate and the rate of increase in internal resistance were calculated similarly to Example 1, except that the battery used was this lithium ion secondary battery. The results are shown in FIG. 1 and FIG. 2 , respectively.
  • the lithium ion secondary batteries of Examples 1 and 2 showed an increase in the capacity recovery rate, and a decrease in the rate of increase in the internal resistance, as compared to the battery of Comparative Example. This is considered to be due to the cooperative effect of the non-aqueous electrolyte solution containing a fluorine-containing material and the use of SiO x as the negative electrode active material.
  • the lithium ion secondary battery of Example 1 showed a higher capacity recovery rate and a lower rate of increase in the internal resistance than the battery of Example 2.
  • the lithium ion secondary battery of Example 2 contains only the fluorine-containing electrolytic salt.
  • FIG. 1 A first figure.

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EP3629400A1 (fr) * 2018-09-28 2020-04-01 Commissariat à l'Energie Atomique et aux Energies Alternatives Procédé de préparation d'oxydes de métaux de transition lithiés
US11515567B2 (en) * 2017-03-17 2022-11-29 Asahi Kasei Kabushiki Kaisha Non-aqueous electrolyte solution, non-aqueous secondary battery, cell pack, and hybrid power system
US11532839B2 (en) 2017-03-17 2022-12-20 Asahi Kasei Kabushiki Kaisha Non-aqueous secondary battery

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CN105895905B (zh) * 2015-02-13 2021-06-22 松下知识产权经营株式会社 电池正极材料和锂离子电池
WO2017110684A1 (fr) 2015-12-22 2017-06-29 日本電気株式会社 Pile rechargeable et son procédé de fabrication
JP7205051B2 (ja) * 2016-12-22 2023-01-17 株式会社Ｇｓユアサ 非水電解質二次電池、及び非水電解質二次電池の製造方法
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US11515567B2 (en) * 2017-03-17 2022-11-29 Asahi Kasei Kabushiki Kaisha Non-aqueous electrolyte solution, non-aqueous secondary battery, cell pack, and hybrid power system
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EP3629400A1 (fr) * 2018-09-28 2020-04-01 Commissariat à l'Energie Atomique et aux Energies Alternatives Procédé de préparation d'oxydes de métaux de transition lithiés

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